The axilla is a fat-filled pyramidal space located between the upper limb and the trunk. It has four walls - anterior, posterior, medial and lateral. Important structures passing through the apex include the axillary vessels and brachial plexus cords. The axilla contains the axillary artery and its branches, axillary vein and tributaries, brachial plexus cords, lymph nodes, and fat. Common issues involving the axilla are shoulder dislocations, lymphadenitis, and thoracic outlet syndrome.

1. AXILLA
By V Subhadra Devi
S E V E N T H
E D I T I O N
Volume 1
Upper Limb
3 V O L U M E S E T

2. • It is a fat filled, pyramidal-shaped space with apex, a base
and four walls
Apex:
• Triangular in shape
• Also called cervico-axillary canal
Boundaries:
• Anterior—posterior border of clavicle
• Posterior—upper border of scapula
• Medial—outer border of 1st rib
• Lateral—coracoid process.
Direction: It is directed upward and medially and continues
into the root of the neck, thereby forming cervicoaxillary canal
Axilla
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

3. Axilla
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

4. Cervico-axillary Canal
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

5. Structures passing through cervico-axillary canal/apex of axilla:
o Axillary vessels
o cords of brachial plexus (both in axillary sheath)
BASE/FLOOR:
Formation:
• It is formed by the skin and the thick layer of axillary fascia
Shape:
• When the arm is abducted, it becomes concave due to pull of
suspensory ligament of axilla
Boundaries:
• Anterior—anterior axillary fold
• Medial—chest wall
• Posterior—posterior axillary fold
Axilla
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

6. Four Walls
1. Anterior Wall - It is formed by
– Pectoralis major—whole extent
– Pectoralis minor—central part
– Subclavius
– Clavipectoral fascia
– Suspensory ligament of the axilla
2. Posterior Wall - It is formed by
– Scapula
– Subscapularis in upper part
– Teres Major in middle part
– Latissimus dorsi in lower part
Axilla– Four Walls
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

7. Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers

8. 3. Medial Wall - It is convex and formed by
– Upper five ribs
– Intercostal muscles in the upper four intercostal spaces
– Serratus anterior muscle—upper 4 or 5 digitations
– Long thoracic nerve
– Intercostobrachial nerve
4. Lateral Wall - It is formed by convergence of anterior and posterior
walls and is formed by
– Upper part of shaft of humerus: Bicipital groove
– Posterior (teres major) axillary folds.
– Biceps brachii: Long head
– Coracobrachialis
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers
Axilla– Four Walls

9. 1. Axillary artery and its six branches.
2. Axillary vein and its tributaries
3. Brachial plexus (infraclavicular part): 3 cords, 13 branches
4. Long thoracic nerve
5. Intercostobrachial nerve
6. Axillary group of lymph nodes
7. Loose areolar tissue with axillary pad of fat
8. Axillary tail of Spence in female adult mammary gland
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers
Contents

10. • Dislocation of shoulder results in damage to the neurovascular structures in the
axilla.
• Axillary lymphadenitis due to infections or malignancy of limb, breast and
abdominal wall above umbilicus.
• Compression of long thoracic nerve of Bell by enlarged central group of axillary lymph
nodes can result in paralysis of serratus anterior muscle.
• Thrombosis of axillary vein because of prolonged hyperabducted arm, e.g. in painting or
plastering the ceiling, postoperative mastectomy with removal of axillary lymph nodes can
lead to venous stasis and edema of upper limb.
• Thoracic outlet syndrome: Compression of vessels and nerves in axilla between clavicle,
1st rib and scapula is called thoracic outlet syndrome.
• Surgical approach to axilla: The medial and posterior walls of the axilla have bones covered
with muscles; the lateral wall is bony; and only the anterior wall is devoid of bones and is
fleshy or covered with muscles only and the base is facial (axillary fascia). Hence,
approaches to axilla are usually through the anterior wall or through the base. The usual
surgical procedures in the axilla are drainage of an axillary abscess or removal of an axillary
lymph node.
Inderbir Singh’s Textbook of Anatomy, 7/e by V Subhadra Devi
© Jaypee Brothers Medical Publishers
Clinical Importance